Study Of The Thermal And Humidity Physical Properties Of Permeable Underlying Surface For Enhancing Thermal Comfort In Outdoor Activity Space

In the context of rapid urban development,the accelerated change of the urban underlying,the reduction of green areas,the increase in anthropogenic heat emissions and pollution from urban activities have made the city ’hyperthermia’,The uncomfortable environment become a constraint to the further development of the city and the improvement of people’s quality of life.Increasing greenery and waters is an effective means of improving the thermal environment,but some outdoor activity sites,whose main function is to provide rest and recreation or traffic access,are unnecessary for waters such as fountains and pools as landscapes on limited sites.Many cities use traditional concrete or asphalt as underlying materials for activity space,however,the hard surface made of these materials can also cause ecological problems for the city after strong heat reflection in summer.Permeable pavements are a hot topic nowadays and have a good performance in mitigating the urban heat island effect,which undoubtedly presents an effective solution to improve the thermal environment and thermal comfort of small urban activity space.In this paper,from the perspective of improving the thermal environment of outdoor activity space and enhancing human thermal comfort,to research the effects of the thermal and humidity physical properties(saturated water content,porosity,reflectivity and evaporation)of permeable pavements on the thermal environment of activity space,to explore the best configuration for their application in event venues to enhance human thermal comfort.Firstly,summarize the application,structure and performance of permeable pavements at home and abroad,as well as the concept and evaluation index of human thermal comfort;then,through existing research,experiments on the thermal and humidity physical properties of permeable pavements are conducted to analyse their effects on the thermal environment and provide a basis for numerical simulations;subsequently,describe the layout principle and simulation process of ENVI-met microclimate simulation software,and based on the experimental data to build site model and set simulation parameters form three aspects(underlying material type,dry or waterish state,greening arrangement).In the end,the visualization results of physiological equivalent temperature(PET)and predicted mean vote(PMV)were combined to analyse the effect of different models on the improvement of the thermal environment and thermal comfort of the event venue,and to conclude the most reasonable configuration applicable to the activity space.The results of research shows that(1)in the study of the correlation between the thermal and humidity physical properties of permeable pavements,it is found that the greater the porosity and saturated water content of the permeable pavement material,the smaller the reflectivity,and that the reflectivity is smaller in the wet state compared to the dry state.(2)In comparing the environmental impact of permeable and non-permeable pavements,it was found that permeable materials have higher surface temperature and lower average radiation temperature at a certain height compared to non-permeable materials.(3)Numerical simulations revealed that a combination of optimization factors(low reflectivity + humidity + shade configuration)was the most effective way to improve the thermal environment and enhance thermal comfort at the event site.Therefore,the large porous permeable pavement can be kept moist by spraying in summer,while the surrounding configuration of greenery is a strategy to improve the thermal environment and enhance the thermal comfort of the activity space.The results of the study provide a theoretical basis for improving the thermal environment of outdoor activity sites,while the research on thermal environment and human thermal comfort is key to a series of issues related to urban environmental quality,human living environment and energy consumption,and has far-reaching significance for achieving sustainable development and improving the quality of urban environment.